Portion of heat sink



FIG. 1 is a front, top and right side perspective view of a portion of heat sink showing our new design;

FIG. 2 is a front elevational view thereof, the rear elevational view being symmetrical with that shown;

FIG. 3 is a right side elevational view thereof, the left side being symmetrical with that shown;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is an enlarged cross-sectional view thereof, taken along line 6—6 of FIG. 2.

The broken-line disclosure in the views is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a portion of heat sink, as shown and described. 